Activatable dental appliance

ABSTRACT

An activatable dental appliance. A concave trough conforms to a plurality of teeth when placed over the plurality of teeth. A first force applying region is configured to apply a first force to at least one tooth of the plurality of teeth for repositioning the tooth. A second force applying region is configured to be selectively activated, wherein when selectively activated the second force applying region applies a force to at least one tooth of the plurality of teeth.

FIELD

Embodiments of the present invention relate in general to the field oforthodontics.

BACKGROUND

Orthodontic treatments involve repositioning misaligned teeth andimproving bite configurations for improved cosmetic appearance anddental function. Repositioning is often accomplished by applying lightcontinuous forces to a patient's teeth over an extended period of time.As part of the process of moving from the initial dental configurationto the final desired end configuration, the teeth typically undergo atransition through a series of intermediate configurations.

Conventionally, repositioning of teeth has been accomplished by what arecommonly referred to as “braces.” Braces comprise a variety of appliancecomponents such as brackets, bands, archwires, ligatures, and O-rings.After the brackets and bands are affixed or bonded to the teeth,periodic meetings with the orthodontist are required so that theorthodontist can reactively adjust the archwires to create a newdirectional forces that continue to move the teeth closer to the desiredposition. This may involve installing different archwires havingdifferent force-inducing properties, adjusting the shape of thearchwires, and/or replacing or tightening the ligatures that secure thewire to the fixed appliance.

An alternative to braces includes the use of aligner-type dentalappliances for realigning teeth. Such an appliance may be comprised of athin shell of material that forms a receiving cavity geometry thatgenerally conforms to a patient's teeth but is slightly out of alignmentwith the initial tooth configuration. Placement of the dental appliancesover the teeth applies controlled forces in specific locations togradually move the teeth into a new predetermined configuration.Repetition of this process with successive appliances comprising newconfigurations eventually moves the teeth through a series ofpredetermined intermediate arrangements along the most effective andefficient treatment path to a final predetermined arrangement.

Aligner-type dental appliances may only be effective over a certainperiod of time due to the limited effective range of the activecomponents of the appliance. After a certain time, the usefulness of thedental appliance is reduced by moving the teeth to the desired location,by a loss in resiliency in the dental appliance, or a combination of thetwo. Once the usefulness of the aligner dental appliance is reduced, thedental appliance is typically disposed of, and the next dental appliancein the treatment series is used. Hence, the shorter the useful lifespanof the dental appliance, the more frequently the dental appliance needsto be changed or adjusted. Consequently, a reduction in the lifespan ofthe dental appliance can require a greater number of dental appliancesto achieve a desired dental result.

SUMMARY

An activatable dental appliance is described herein. In one embodiment,the activatable dental appliance comprises a concave trough thatconforms to a plurality of teeth when placed over the plurality ofteeth. A first force applying region is configured to apply a firstforce to at least one tooth of the plurality of teeth for repositioningthe tooth. A second force applying region is configured to beselectively activated, wherein when selectively activated the secondforce applying region applies a force to at least one tooth of theplurality of teeth.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a jaw with an incremental position adjustment dentalappliance upon which embodiments of the present invention may beimplemented.

FIG. 2A illustrates an activatable dental appliance including an activeregion and a passive region, in accordance with one embodiment.

FIG. 2B illustrates interaction of an activatable dental appliance and atooth, in accordance with one embodiment.

FIG. 2C illustrates example indications for indicating a location of apassive region of an activatable dental appliance, in accordance withembodiments.

FIG. 3A illustrates a top-down cut-away view of an activatable dentaltray including a passive region prior to activation, in accordance withan embodiment.

FIG. 3B illustrates a top-down cut-away view of an activatable dentalappliance including an activated passive region, in accordance with anembodiment.

FIG. 4A illustrates a top-down cut-away view of interaction between atooth and an activatable dental appliance including a passive regionprior to activation, in accordance with an embodiment.

FIG. 4B illustrates a top-down cut-away view of interaction between atooth and an activatable dental appliance including an activated passiveregion, in accordance with an embodiment.

FIG. 4C illustrates a top-down cut-away view of interaction between atooth and an activatable dental appliance including an activated passiveregion after tooth movement, in accordance with an embodiment.

FIG. 5 is a flow chart of a method for repositioning teeth, inaccordance with one embodiment.

FIG. 6 is a flow chart of a method for fabricating a dental appliancefor repositioning at least one tooth, in accordance with one embodiment.

DESCRIPTION OF EMBODIMENTS

In the following description, numerous specific details are set forth inorder to provide a thorough understanding. However, it will berecognized by one of ordinary skill in the art that embodiments may bepracticed without these specific details. In other instances, well knownmethods, procedures, and components have not been described in detail asnot to unnecessarily obscure aspects of the present invention.

Overview

Embodiments in accordance with the present invention extend the usefullifespan of the dental appliance by including additional activatableforce regions that can be activated after the initial forces have beendepleted.

Specifically, various embodiments disclose an activatable dentalappliance. The activatable dental appliance comprises a concave troughwhich conforms to a plurality of teeth when placed over the plurality ofteeth. In other words, upon placement, controlled forces are applied tothe teeth as the appliance conforms in specific locations to graduallymove the teeth into a new predetermined configuration. A first forceapplying region (e.g., a specific location), is configured to apply afirst force to at least one tooth for repositioning the tooth. The firstforce is applied by the dental appliance in a standard manner. However,in one embodiment, once the useful lifespan of the dental appliance issufficiently exhausted, a second force applying region(s) is/areselectively activated. When selectively activated the second forceapplying region(s) applies a force to at least one tooth of theplurality of teeth. Hence, a second force can be selectively activatedin a dental appliance once the first force generated by the dentalappliance is no longer useful. Accordingly, embodiments of the presentinvention provide an activatable dental appliance that extends the lifeand usefulness of the dental appliance.

System and Method for Positioning Teeth

As is known in the art, in order to fabricate an incremental positionadjustment dental appliance, an initial digital data set (IDDS)representing an initial tooth arrangement and a final digital data set(FDDS) representing a final tooth arrangement are generated. Based onboth the IDDS and the FDDS, a plurality of intermediate digital datasets (INTDDSs) are defined to correspond to incrementally adjusteddental appliances. The INTDDSs are defined using techniques for aligningteeth that can mimic how the teeth might move if treated with fixedorthodontic appliances. Thereafter, a set of incremental positionadjustment dental appliances are produced based on the INTDDs and theFDDS. The dental appliances are designed to be worn over the teeth andto reposition the teeth to each of the tooth arrangements.

Referring now to FIG. 1, a single adjustment dental appliance 110 whichis worn by the patient in order to achieve an incremental repositioningof a lower jaw 100 is shown. The dental appliance 110 is one of a seriesof incremental position adjustment dental appliances worn by the patientto realign teeth from an initial arrangement to a final arrangement.

The example dental appliance 10 comprises a polymeric shell having acavity shaped to receive and resiliently reposition teeth from one tootharrangement to a successive tooth arrangement. In one embodiment, thepolymeric shell will fit over all teeth present in the upper or lowerjaw. On occasion, only certain one(s) of the teeth will be repositionedwhile others of the teeth will provide a base or anchor region forholding the dental appliance in place as it applies the resilientrepositioning force against the tooth or teeth to be repositioned.Certain areas of the appliance will confer orthodontic forces on theteeth due to the intentional mismatch built into the appliance betweenthe tooth's current position and the desired position built into theappliance. These are the inherently “active” regions of the appliance.Certain areas of the appliance will conform to the teeth nearly exactlyas they are, without introducing orthodontic forces onto the teeth towhich they conform. These are the inherently “passive” areas of theappliance which retain the teeth as they are in their current state.

The planning and fabrication of such dental appliances as an exampleelastic polymeric positioning appliance is described in detail in U.S.Pat. No. 5,975,893, and in published PCT application WO 98/58596 whichdesignates the United States and which is assigned to the assignee ofthe present application. Systems of dental appliances employingtechnology described in U.S. Pat. No. 5,975,893, are commerciallyavailable from Align Technology, Inc., Santa Clara, Calif., under thetradename, Invisalign System. Align Technology, Inc., is the assignee ofthe present application.

Activatable Dental Appliance

Throughout the body of the Description of Embodiments, the use of theterms “aligner” or “dental aligner” is synonymous with the use of theterms “appliance” and “dental appliance” in terms of dentalapplications. For purposes of clarity, embodiments are hereinafterdescribed within the context of the use and application of dentalappliances, and more specifically “dental appliances.”

FIG. 2A illustrates an activatable dental appliance 210 including anactive region 215 and a passive region 220, in accordance with oneembodiment. Activatable dental appliance 210 includes a concave troughthat generally conforms to a patient's teeth but is slightly out ofalignment with an initial or immediately prior tooth configuration. Theslight misalignment is caused by active region 215 and is for applying apredetermined force to a tooth in a predetermined direction for movingat least one tooth to a desired location. It should be appreciated thatactive region 215 and passive region 220 are established prior toformation of activatable dental appliance 210.

The “activatable” portion of the appliance is the area of the devicethat begins passive but becomes active as a result of user activation ofthe device. The appliance furthermore, is activatable, because of arelief portion built into the appliance that will accommodate the toothmovement once the appliance is activated. In one embodiment, an area ofrelief is built into the appliance in anticipation of the desired toothmovement. Furthermore, the area(s) on the appliance that can beadjustable are indicated such that the user can identify precisely thelocations on the appliance where adjustments should be positioned.

Specifically, FIG. 2A shows activatable dental appliance 210 includingpassive regions 220, 222, 224, 226, 228 for the purpose of moving atooth upon activation in the course of orthodontic treatment.Activatable dental appliance 210 is shaped to receive and resilientlyreposition a patient's dentition. For example, the active region 215 mayapply a first force to a tooth for purposes of repositioning the tooth.

Moreover, dental appliance 210 includes a space for providing anunobstructed path for avoiding interferences between the path of toothand the appliance when repositioning a tooth. For example, dentalappliance 200 may include a space on the opposite side of the tooth frompassive region 220. Upon activation, force exerted by activating passiveregion 220 may reposition the tooth into the space. The absence ofinterference enables the tooth to move from its current position to thedesired position once the appliance is activated. This is importantbecause interference by the appliance can prevent a tooth from moving tothe desired final position.

It should be appreciated that active region 215 may generate a forceoriented in any direction depending on the direction of desiredrepositioning, such as and without limitation, rotation, translation,inclination, angulation, intrusion, and extrusion. That is, thegenerated force can be a translational or rotational force along any ofthe tooth's directional axes or any combination of these directions, invarious embodiments.

Passive region 220, upon activation into an active region, may apply asecond force to a tooth. Similarly, one or multiple passive regions220-228 on a single tooth, upon activation into an active region, maygenerate a one or more forces in any direction. For example, byactivating passive regions 226 and 228, simultaneously, the respectivetooth would rotate and possibly extrude the tooth, depending on theirrelationship to each other and the tooth contour. If regions 220 and 222were activated simultaneously, the respective tooth would likelytranslate and possibly tip.

It should be appreciated that dental appliance 210 may include anynumber of active regions and passive regions. In addition, passiveregions 220-228 can be activated in any order, and can exert forcesconcurrently or sequentially, depending on the needs of the orthodontictreatment. Furthermore, it should be appreciated that passive regionsmay overlap, such that two passive regions apply forces to the samelocation in sequential incremental repositionings (not shown). It isimportant to note that an appliance may be completely passive and onlymoves teeth upon activation of one or more regions. Or there may beactive regions in conjunction with activatable regions within the sameappliance. It should also be appreciated that in one embodiment activeregion 215 resides on a buccal side and a passive region (e.g., passiveregion 220) resides on a lingual side of the same tooth. Moreover,active region 215 may reside adjacent to the gingiva and the passiveregion may reside adjacent to the cusp of the same tooth.

In one embodiment, activatable dental appliance 210 is designeddigitally as a three-dimensional (3D) model prior to being manufactured.For example, activatable dental appliance 210 is based at least on aplurality of INTDDSs as described above. At least two sequential INTDDSsare digitally merged, where the first INTDDS is associated with forcesgenerated by active region 215 and where the second INTDDS is associatedwith forces generated upon the activation of passive region 220. The 3Dmodel can be tested prior to manufacture for digitally testing theforces exerted by active region 215 and passive region 220 uponactivation. In addition to the merging of the sequential INTDDS, theunion geometric path taken between one INTDDS and the subsequent INTDDSis defined such that the tooth to be moved can be done in such a waywhere the tooth is unobstructed by the appliance if moved from thecurrent to the desired state. This allows the activation of theappliance to move the tooth in an unobstructed manner, free ofinterference between the tooth and the appliance in its intended path.

FIG. 2B illustrates interaction of an activatable dental appliance and atooth, in accordance with one embodiment of the present invention. Asshown in FIG. 2B, a partial representation of activatable dentalappliance 210 is shown being worn over the patient's dentition. Inparticular, activatable dental appliance 210 is shown being worn overthe tooth 230. In an initial configuration, active region 215 applies aforce to tooth 230 for purposes of repositioning, and passive region 220is not activated, and thus applies no force to tooth 230.

Active region 215 applies a repositioning force to tooth 230, forinstance, to move tooth 230 closer to tooth 240 for reducing gap 250. Asshown, active region 215 applies a force to tooth 230 in a combinedtranslational force towards tooth 240 and a lingual direction forcetowards the tongue. As described above, active region 215 applies aforce for incrementally repositioning a tooth, and only applies theforce for a certain period of time. That is, the force stored within adental appliance may only be effective for a given time period, e.g.,one or two weeks.

Embodiments of the present invention provide for activating passiveregions of activatable dental appliance 210, such that additional forcescan be generated for repositioning a tooth, thereby extending the lifeand usefulness of dental appliance 210. For example, activating passiveregion 220 causes a second force to be applied to tooth 230 to movetooth 230 closer to tooth 240 for reducing gap 250. As shown, uponactivation, region 220 applies a force for incrementally repositioningtooth 200 in a combined translational force towards 240 and a facialdirection towards the side of the mouth.

It should be appreciated that a passive region such as passive region220 can be activated in many different ways. For instance, and withoutlimitation, passive region 220 may be activated using an activationtool, such as pliers. It may be necessary to heat the activation tool toallow activatable dental appliance 210 to deform for activation ofpassive region 220. In another embodiment, passive region 220 may beactivated by a finger applying pressure to the passive region to createa force applying bump.

In various embodiments, in order to ensure that passive region 220 isproperly activated, activatable dental appliance 210 includes anindication for indicating a location of passive region 220. FIG. 2Cillustrates example indications. For example, indication 260 includes anouter circle and an inner circle, and indication 262 includes an outercircle and an “X”. It should be appreciated that passive regions neednot be circular, but rather can be any shape. Indication 264 illustratesan elliptical shaped passive region, and includes a straight line.Indications 260, 262 and 264 may be printed or placed on dentalappliance 210. It should be appreciated that indications 260, 262 and264 are examples, and that activatable dental appliance 210 can includean indication of all different shapes and sizes.

It should be appreciated that the indication may also indicate how todeform activatable dental appliance 210 for properly activating passiveregion 220. For example, with reference to indication 260, dentalappliance 210 may be deformed such that the inner circle is depresseduntil deformation extends to the outer circle. Similarly, with referenceto indication 264, the line may be depressed until deformation extendsto the outer ellipse.

In other embodiments, the indication is a bump 310 a on the outersurface of the dental appliance 300 that is activated to become a bumpon the inner surface of the dental appliance. FIGS. 4A and 4B illustratethe activation of a passive bump on the outer surface of an activatabledental appliance.

As shown in the embodiment of FIG. 3A, activatable dental appliance 300includes passive bump 310 a. In an initial state, passive bump 310 aextends out from the outer surface of dental appliance 300. It should beappreciated that passive bump 310 a is established prior to formation ofactivatable dental appliance 300. Passive bump 310 a is activated bypressing bump 310 a into dental appliance 300. Although passive bump 310a is shown on the buccal side of a tooth, it may be located on thelingual side as well (see FIG. 2A).

As shown in FIG. 3B, upon activation, active bump 310 b extends intodental appliance 300. In an activated state, upon placing dentalappliance 300 over the patient's dentition, active bump 310 b applies aforce to a tooth. It should be appreciated that bump 310 b may be ofsuch a shape to apply a specific force. For instance, a larger bump mayprovide a larger force on a tooth, depending on the location andorientation of the bump.

While the indication is described in detail herein as being printed onthe dental appliance or a bump formed within the dental appliance, itshould be appreciated that others forms of indicia may be used. Forexample, an indentation or series of indentations may be formed orstamped into the activatable dental appliance for indicating thelocation of the passive region.

FIGS. 4A-C illustrate the interactions of an activatable dentalappliance on a tooth. Specifically, FIGS. 4A-C illustrate the movementof a tooth through the use of forces generated by activating a passivebump on the outer surface of the dental appliance in the course oforthodontic treatment.

As shown in FIG. 4A, activatable dental appliance 400 includes passivebump 410 a. Dental appliance 400 generally conforms to teeth 420, 422and 424 of a patient's dentition. In an initial state, passive bump 410a extends out from the buccal or outer surface of dental appliance 400.It should be appreciated that passive bump 410 a is established prior toformation of activatable dental appliance 400. Passive bump 410 a isactivated by pressing bump 410 a into dental appliance 400. Moreover,dental appliance 400 includes space 430 for providing an unobstructedpath for avoiding interferences in repositioning tooth 422. As shown,space 430 is on the opposite or lingual side of tooth 422 as bump 410 a.

As shown in FIG. 4B, upon activation, active bump 410 b extends intodental appliance 400. In an activated state, active bump 410 b applies aforce to tooth 422, where the direction of force is indicated by arrow415. It should be appreciated that bump 410 b may be of such a shape toapply a specific force. For instance, a larger bump may provide a largerforce on a tooth, depending on the location and orientation of the bump.The force as indicated by arrow 415 repositions tooth 422, directingtooth 422 into space 430. As mentioned earlier, an alternativeembodiment may include the bump 410 b having still another bump thatwould surround bump 410 b, so that when activated would further extendbump 410 b against the tooth 422 to create a new force at the same ornear same location as bump 410 a.

FIG. 4C illustrates dental appliance 400 where active bump 410 b hasmoved tooth 422 such that bump 410 b no longer applies any force totooth 422. Accordingly, space 430 has been reduced, as tooth 422 hasmoved into space 430.

FIG. 5 is a flow chart of a method 500 for repositioning teeth, inaccordance with one embodiment of the present invention. The presentembodiment provides an activatable dental appliance includingactivatable force applying regions. As such, embodiments of the presentinvention are capable of providing multiple stage incrementalrepositioning of teeth.

At step 510, the present embodiment provides a polymeric shell dentalappliance of a type that is removably placeable over a patient'sdentition. The appliance includes a concave trough which conforms to aplurality of teeth when placed over the patient's dentition, andincludes a geometry for repositioning the plurality of teeth from afirst tooth arrangement to a second tooth arrangement. For illustration,FIGS. 3A and 3B show an activatable dental appliance 210. Active region215 at least in part defines the geometry for repositioning tooth 230.

Subsequently, as shown at step 520, an activatable force applying regionof the appliance is activated such that the appliance includes a secondgeometry for repositioning the plurality of teeth from the second tootharrangement to a third tooth arrangement. For illustration, withreference to FIG. 2B, passive region 220 at least in part defines thesecond geometry for further repositioning tooth 230.

In one embodiment, as shown at step 522, an activation tool is used toactivate the activatable force applying region. In another embodiment,as shown at step 524, a finger is used to activate the activatable forceapplying region

FIG. 6 is a flow chart of a method 600 for fabricating a dentalappliance for repositioning at least one tooth, in accordance with oneembodiment of the present invention. The present embodiment provides anactivatable dental appliance including activatable force applyingregions. As such, embodiments are capable of providing multiple stageincremental repositioning of teeth.

At step 610, a computer-generated model of a patient's teeth is created.For illustration, a 3D computer model of jaw 100 of FIG. 1 is generated.A computer simulation is capable of modeling interactions among theteeth on jaw 100. The 3D model can be used to simulate jaw movementsincluding protrusive motions, lateral motions, and “tooth guided”motions where the path of lower jaw 100 is guided by teeth contactsrather than by anatomical limits of jaw 100. Motions are applied to onejaw, but may also be applied to both the lower and upper jaws. Based onthe computer-generated model, the final arrangement of the teeth in jaw100 can be ascertained.

At step 620, a plurality of successive incremental tooth arrangements ofthe patient's teeth are determined, wherein an incremental tootharrangement comprises repositioning at least one tooth. As describedabove, a plurality of INTDDSs are defined to correspond to incrementallyadjusted dental appliances. The INTDDSs are defined using techniques foraligning teeth, which in general, mimic the way that teeth move whenfixed orthodontic brackets and wires are used. However, unlike thereactive process of conventional bracket and wire orthodontics,predetermined INTDDSs are defined to provide a specific force along themost effective treatment path.

At step 630, at least two of the successive incremental tootharrangements are merged and the union of the path from one arrangementto the successive arrangement determined. The merging of two successiveincremental tooth arrangements allows for determining active forceapplying regions and activatable force applying regions for each tooth.For illustration, FIG. 2A shows activatable digital appliance 210 basedat least on a plurality of INTDDSs as described above. At least twosequential INTDDSs are digitally merged, where the first INTDDS isassociated with forces generated by active region 215 and where thesecond INTDDS is associated with forces generated upon the activation ofpassive region 220. The 3D model can be tested for digitally testing theforces exerted by active region 215 and passive region 220 uponactivation. For example, forces exerted by active region 215 and passiveregion 220 upon activation are applied to the 3D model for testing themovement of the teeth to a new position.

At step 650, an indication for indicating a location on the appliancefor activating the activatable force applying region is created.Thereafter, an appliance is fabricated. The appliance conforms to thepatient's teeth and includes at least one activated force applyingregion for repositioning at least one tooth, includes at least oneactivatable force applying region for repositioning at least one toothupon activation, and includes space for providing an unobstructed pathfor avoiding interferences in repositioning at least one tooth.

While the embodiments illustrated in methods 500 and 600 show specificsequences and quantity of steps, the present invention is suitable toalternative embodiments. For example, not all the steps provided for inthe methods are required for the present invention. Furthermore,additional steps can be added to the steps presented in the presentembodiment. Likewise, the sequences of steps can be modified dependingupon the application.

Embodiments of the present invention, an activatable dental appliance,have been described herein. While the invention is described inconjunction with various embodiments, it is understood that they are notintended to limit the invention to these embodiments. On the contrary,the invention is intended to cover alternatives, modifications andequivalents, which may be included within the spirit and scope of theinvention as defined by the appended claims.

1. An activatable dental appliance comprising: a concave troughconforming to a plurality of teeth when placed over the plurality ofteeth; a first force applying region configured to apply a first forceto at least one tooth of the plurality of teeth for repositioning thetooth when the trough conforms; and a second force applying regionconfigured to be selectively activated, wherein when selectivelyactivated the second force applying region applies a force to at leastone tooth of the plurality of teeth; wherein the first force applyingregion and the second force applying region are established prior toformation of the appliance.
 2. The dental appliance of claim 1, whereinthe second force applying region comprises an indication for indicatinga location in the appliance for activating the second force applyingregion.
 3. The dental appliance of claim 2, wherein the indication is abump on an outer surface of the appliance until activated to become abump on an inside surface of the appliance.
 4. The dental appliance ofclaim 3, wherein the bump is of such a shape to apply a specific force.5. The dental appliance of claim 4, wherein the shape of the bump issuch to provide a third force to a single tooth when activated.
 6. Thedental appliance of claim 1, further including at least a third forceapplying region.
 7. The dental appliance of claim 6, wherein the thirdforce applying region is applied to the same tooth as the second forceapplying region.
 8. The dental appliance of claim 6, wherein the thirdforce applying region applies a force to the same location as the secondforce applying region.
 9. The dental appliance of claim 7, wherein thethird force applying region applies a force to a tooth location on theopposite side of the same tooth.
 10. The dental appliance of claim 6,wherein the third force applying region is activated at the same time asthe second force applying region.
 11. The dental appliance of claim 1,wherein the appliance is designed digitally as a 3D model before beingmanufactured.
 12. The dental appliance of claim 1, wherein the secondforce applying region is operable for activation by an activation tool.13. The dental appliance of claim 1, wherein the second force applyingregion is operable for activation by a finger.
 14. The dental applianceof claim 1, wherein the second force applying region is operable foractivation by distorting the appliance proximate the second forceapplying region.
 15. The dental appliance of claim 1, further comprisinga space within the trough for providing an unobstructed path foravoiding interferences in repositioning at least one tooth of theplurality of teeth.
 16. The dental appliance of claim 15, wherein thespace is on a tooth side that is opposite to the side that contains thesecond force applying region, wherein the second force applied to thetooth moves the tooth into the space.
 17. The dental appliance of claim1, wherein the first force applying region and the second force applyingregion upon activation apply a force to the same tooth of the pluralityof teeth.
 18. The dental appliance of claim 17, wherein the movement isselected from the group consisting essentially of: rotation, translate,tilt, impound, and extract.
 19. The dental appliance of claim 17,wherein the first and second force move the at least one tooth in thesame direction.
 20. The dental appliance of claim 1, wherein the firstforce applying region and the second force applying region uponactivation apply a force to different teeth of the plurality of teeth.21. The dental appliance of claim 1, wherein the first force applyingregion resides on a buccal side and the second force applying regionresides on a lingual side of the at least one tooth.
 22. The dentalappliance of claim 21, wherein the first force applying region residesadjacent to the gingiva and the second force applying region residesadjacent to the cusp of the at least one tooth.
 23. A method forrepositioning teeth, the method comprising: providing a polymeric shelldental appliance of a type that is removably placeable over a patient'sdentition, the appliance comprising a concave trough which conforms to aplurality of teeth when placed over the patient's dentition, theappliance comprising a geometry for repositioning the plurality of teethfrom a first tooth arrangement to a second tooth arrangement; andsubsequently, activating an activatable force applying region of theappliance such that the appliance comprises a second geometry forrepositioning the plurality of teeth from the second tooth arrangementto a third tooth arrangement, wherein the activatable force applyingregion is established prior to formation of the appliance.
 24. Acomputer-implemented method for fabricating a dental appliance forrepositioning at least one tooth, the method comprising: creating acomputer-generated model of a patient's teeth; determining a pluralityof successive incremental tooth arrangements of the patient's teethwherein an incremental tooth arrangement comprises repositioning atleast one tooth; merging at least two of the plurality of successiveincremental tooth arrangements; and fabricating the appliance to conformto the patient's teeth and to comprise at least one activated forceapplying region for repositioning at least one tooth, to comprise atleast one activatable force applying region for repositioning at leastone tooth upon activation, and to comprise space for providing anunobstructed path for avoiding interferences in repositioning at leastone tooth.
 25. A system for repositioning teeth comprising: means forcreating a computer-generated model of a patient's teeth; means fordetermining a plurality of successive incremental tooth arrangements ofthe patient's teeth wherein an incremental tooth arrangement comprisesrepositioning at least one tooth; means for merging at least two of theplurality of successive incremental tooth arrangements; and means forfabricating the appliance to conform to the patient's teeth and tocomprise at least one activated force applying region for repositioningat least one tooth, to comprise at least one activatable force applyingregion for repositioning at least one tooth upon activation, and tocomprise space for providing an unobstructed path for avoidinginterferences in repositioning at least one tooth.